Cancer Chemoprevention by Retinoids and Carotenoids: Proposed Role of Gap Junctional Communication
Maryce M. Jacobs in Vitamins and Minerals in the Prevention and Treatment of Cancer, 2018
The prevention of disease should always be the primary goal of medical science, indeed many of the successes of 20th century medicine have come through the prevention of infectious disease rather than the treatment. Epidemiologic studies have firmly established that diet and tobacco contribute to approximately 70% of excess cancer in the US population. Not all aspects of the diet are deleterious; consumption of fruits and vegetables rich in carotenoids have frequently been associated with a lower risk of cancer. The similarity of biological action of retinoids and carotenoids in inhibiting neoplastic transformation suggests that these compounds share similar molecular mechanisms of action. The enhancement of junctional permeability induced by retinoids correlated with the inhibition of transformation, and vice versa. Recent studies have shown that carotenoids such as ß-carotene and canthaxanthin elevate junctional communication as dramatically as do the retinoids.
Skin
A. Sahib El-Radhi in Paediatric Symptom and Sign Sorter, 2019
Normal skin colour is mostly determined by the child's constitutional degree of melanin content of the skin resulting from hereditary and racial backgrounds. Pallor or reduced or loss of the colour of skin or mucous membrane can be caused by a variety of conditions including normal complexion, lack of exposure to sunlight, anaemia, emotional stress, shock or chronic disease. Cyanosis is caused by the presence of an excess of deoxygenated haemoglobin which is visible in the skin and mucous membranes. Pigmentary disorders are a common presentation to family physicians, paediatricians and dermatologists. Melanin plays key roles in determining human skin colour. Mastocytosis is a group of disorders that are characterised by an accumulation of mast cells in the skin and other organs. Carotenaemia – yellow discolouration of the infant skin by the pigment carotene – is often mistaken as jaundice. Albinism is a hypopigmented disorder involving the skin, hair and iris.
Oral Cavity Cancer
Dongyou Liu in Tumors and Cancers, 2017
Various tumors are known to affect the oral cavity, the most important of which are squamous cell carcinoma (SCC), verrucous carcinoma, basal cell carcinoma (BCC), and lymphoma. The oral cavity is an oval-shaped structure demarcated by the lips anteriorly, the cheeks laterally, the floor of the mouth inferiorly, the palate superiorly, and the oropharynx posteriorly. Oral SCC often looks like scaly red patches, open sores, elevated growths with a central depression, or warts on the lip or lateral part of the tongue. Standard treatments for oral cavity cancer are surgery and radiotherapy. Risk factors for oral cavity cancer include tobacco smoking/chewing, alcohol drinking, betel quid or gutka chewing, diet low in beta-carotene-rich vegetables and citric fruits, poor oral health, infection with Candida albicans, human herpes virus, and human papillomavirus, exposure to sunlight or UV, premalignant lesions and other oral conditions, and immunosuppression.
Evaluation of retinal susceptibility to light damage in pigmented rats supplemented with beta-carotene
Published in Current Eye Research, 1996
Laurence M. Rapp, Patricia L. Fisher, Donny W. Suh
The present study evaluated the influence of beta-carotene supplementation on the susceptibility of the retina to light damage. Long-Evans pigmented rats were supplemented with beta-carotene by either dietary or intraperitoneal administration, and beta-carotene levels in plasma, liver and retina were determined by high performance liquid chromatography. Other animals from each group were exposed to ultraviolet-A light at a dose of 8.1 J/cm2 in their right eye only, and photoreceptor cell losses determined by light microscopic morphometry. In supplemented animals, beta-carotene levels increased markedly in the liver, and were elevated from non-detectable to detectable in the plasma and retina, relative to nonsupplemented controls. In each tissue, beta-carotene levels were found to be higher in animals receiving intraperitoneal supplementation as compared to dietary. Beta-carotene supplementation by either route did not protect the retina against photoreceptor cell loss measured at two weeks following UVA exposure. Preliminary observations indicated that beta-carotene supplementation decreased the incidence of light-induced retinal pigment epithelium destruction.
Solubilization of β‐carotene in culture media
Published in Nutrition and Cancer, 1997
Myron Gross, Thomas Bishop, John Belcher, David Jacobs
Several methods were evaluated for the solubilization of supraphysiological concentrations of β‐carotene in culture media. The addition of β‐carotene in ethanol as 0.1 % (vollvol) of culture medium that contained 10% fetal bovine serum and incubation at 37°C for 30 minutes solubilized approximately 50% of the added carotenoid. Solubilized β‐carotene concentrations from 3.06 to 36.4 μmol/l were obtained by this method. Ultracentrifugation studies localized the solubilized β‐carotene to low‐density lipoproteins (67.0%) and high‐density lipoproteins (24.9%). Other methods utilizing various amounts of fetal bovine serum, ethanol, and hexane as solvents did not significantly improve the solubilization of β‐carotene compared with the use of ethanol as 0.1% (vollvol) of culture medium that contained 10% fetal bovine serum. Nonetheless, solubilization of supraphysiological concentrations of β‐carotene indicated the feasibility of preparing culture media containing physiological concentrations (≈0.5 μmol/l) of β‐carotene.
The effect of β‐carotene on BP‐induced respiratory tract tumors in hamsters
Published in Nutrition and Cancer, 1987
The modifying effect of β‐carotene on benzo[a]pyrene (BP)‐induced tumors of the respiratory tract was investigated in Syrian hamsters. Groups of hamsters were fed a semisynthetic diet supplemented with either no or 56 mg/kg β‐carotene. Respiratory tract tumors were induced by intratracheal instillation of BP attached to ferric oxide. The β‐carotene and vitamin A contents of the liver were increased in the high β‐carotene group, but the serum β‐carotene levels were very low when compared with those commonly observed in humans. β‐Carotene supplementation did not affect the tumor response of the respiratory tract. Neither the incidence and severity of preneoplastic changes were influenced. However, there was a statistically significant inverse relationship between serum retinol content and the presence of respiratory tract tumors in survivors, regardless of the dietary treatment.